In a known tool holder of that kind (German utility model No. 74 38172), the connecting portion has a housing with a radially extending guide. Mounted in the guide is a slider which belongs to the head portion and which is displaceable in a radial direction by means of the screwthreaded spindle. An inside turning or boring tool is fitted into the tool receiving means of the head portion. By rotating the screwthreaded spindle, it is possible to displace the head portion and thus the tool radially with respect to the axis of the shank thereby to alter the working diameter of the tool. That known tool holder is comparatively expensive to produce for the guide and the slider must be machined with a very high degree of accuracy in order to provide a play-free connection between the two components. In addition, by virtue of its design, the known tool holder is only suitable for very fine machining where low cutting forces occur. Another disadvantage of the known tool is also that adjustment of the head portion relative to the connecting portion can only be made in one radial direction. However, in the case of turnover or reversible bit borers which are used for producing bores in solid material, it is not only important that the working diameter of the borer can be altered by adjustment of the borer in a radial direction, but it is also important for the cutting bit which operates in the region of the axial centre line of the workpiece to be so arranged that it intersects the axial centre line of the workpiece. If the cutting edge is too high, then the axial centre line of the workpiece would extend beneath the cutting edge and the workpiece would not be cut in its region directly adjoining its axial centre line. The projecting portion that would then remain would bear against the breast of the effective cutting edge and the latter would then break off as a result of the pressure. If on the other hand the effective cutting edge is too low relative to the axial centre line, then it also leaves behind a small projecting portion. As that projecting portion meets the cutting edge at a highly disadvantageous angle, almost tangentially, it tries to climb up over the cutting edge, whereby its diameter increases. The projecting portion pushes the borer away or a counteracting force is produced, which can also result in the cutting edge breaking. It is therefore important for borers with turnover bits of that kind also to be able to be adjusted in a second direction which is normal to the first radial direction. In addition, reamers or broaches must be so set that their axis precisely coincides with the axial centre line of the workpiece.
The invention is based on the problem of providing a tool holder with radial adjustment means for a tool, in particular a rotary tool, of the kind set forth in the opening part of this specification, which permits radial adjustment of the tool in two mutually perpendicular directions, which is of a simple construction and of small dimensions, and which finally is also suitable for the transmission of high forces.
According to the invention, that is achieved in that an intermediate portion is disposed between the connecting portion and the head portion, that all three portions are of a substantially disc-like configuration and bear against each other with their faces which extend radially with respect to the axis of the connecting shank, that provided at the periphery of the connecting portion are two diametrally oppositely disposed recesses into which two claws arranged on the intermediate portion engage with radial play, that provided at the periphery of the intermediate portion are two diametrally oppositely disposed recesses which are displaced through 90.degree. relative to the claws and into which two claws disposed on the head portion engage with radial play, that the screwthreaded spindle can be screwed in the connecting portion in a first screw-threaded bore extending between the two recesses of the connecting portion and with its ends bears without play against the claws of the intermediate portion, that a further screwthreaded spindle can be screwed in the intermediate portion in a second screwthreaded bore extending normal to the first screwthreaded bore and with its ends bears against two diametrally oppositely disposed inside surfaces of the head portion, and that the screws are provided as clamping screws for pressing together the faces of the three portions.
The novel tool holder permits adjustment of the tool which is fitted into the tool receiving means of the head portion, in two mutually perpendicular radial directions. It is of a simple construction, while the small number of individual components thereof are easy to machine. It is also of comparatively small structural dimensions. In addition, the three disc-like main components of the tool holder are firmly pressed together at their faces by the clamping screws, after the tool has been set, while in addition the claws engage into the respective recesses. Consequently, the novel tool holder is also suitable for transmitting high forces.